It seems to me that those songs that have been any good, I have nothing much to do with the writing of them. The words have just crawled down my sleeve and come out on the page.
In discussing the process with the actors, I made it clear to them that they could improvise but that the sum total of their improvisation needed to impart certain plot points, and schematic material.
It's very clearly stated in the film: You make your own choices, and what you're always fighting is ego.

